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Old 04-07-2011, 09:54 AM   #1
Ed
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Multiple DSC radio operation

Hi all,
This question is submitted for a friend who is not a member of the forum.* He has 2 DSC capable VHFs in his pilothouse that are used to monitor different channels.* He does not want to use scan or multi-channel monitoring to achieve his purpose.* He does want to program his MMSI into both radios so that he has a backup in case of failure of the primary VHF.
*
The question is; How do you manage the DSC response of more than one radio so that the audio DSC alarm on the secondary radio doesn't interfere with the ability to hear the voice traffic on the primary radio?* There doesnt appear to be a firmware defined method to put DSC to sleep or stand-by so that the 2nd radio would not alarm when a DSC call is received.* Has anyone resolved this yet?
*
Thanks,
*
Ed, N7NVP
PT-38 Sedan* "Makin Do"
Brownsville, WA
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Old 04-07-2011, 12:12 PM   #2
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RE: Multiple DSC radio operation

I have two Standard Horizon VHF radios, both with DSC. These radios will alarm and switch to channel 16 when a DSC emergency call comes in. The alarms just about scare you out of the boat! I contacted SH and was told that the radios were designed that way, and could not be changed. I was told by the Icom rep at the boat show that their VHf's could be set to not change channel on a DSC alarm.

I don't plan on buying an Icom so I have an operating plan. I will shut down, (turn off) one of the radios, then deal with the DSC emergency on the other radio.

The USCG has recognized that this auto channel switch can create a hazard such as when a tug or ship is docking and needs continuous communications with the assist tugs. There have already been accidents caused by the auto channel switching.

Best advice is to contact customer tech support for your radio, and determine how or if you can disable the auto switch function. Other than that, plan on shutting down one of the radios to limit the confusion and panic.
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Old 04-07-2011, 01:47 PM   #3
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RE: Multiple DSC radio operation

Quote:



Best advice is to contact customer tech support for your radio, and determine how or if you can disable the auto switch function. Other than that, plan on shutting down one of the radios to limit the confusion and panic.
*Either that or just disconnect one radio from the DSC.

I believe it is the NEMA 0183 wire

*

SD

wiring

*
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Old 04-09-2011, 09:51 AM   #4
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RE: Multiple DSC radio operation

Thanks, guys.* My friend has decided to contact the manufacturer.* If anything enlightening comes out of it I'll post it here.
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Old 04-11-2011, 06:02 AM   #5
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RE: Multiple DSC radio operation

And please realize that DSC is not just for emergency purposes. It is a valuable tool in contacting known boats and switching them to a channel of the caller's choice without having to go through the tedium of hailing and agreeing on a channel. THAT prevents unnecessary radio chatter that actually could interfere with an actual emergency. I have heard an emergency alarm exactly once since DSC proliferated. I have heard numerous emergency calls!!!

The problem with entering the same code into two radios is you have to chase down the other radio to get it to quit alarming. And if you choose to have unique MMSIs, make sure you install the radios in a way that you can determine which one is ringing. We have a buddy that has two identical radios installed one on top of the other and he goes mad trying to figure out which one is ringing...lol.
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Old 04-11-2011, 10:03 AM   #6
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RE: Multiple DSC radio operation

Baker wrote:

The problem with entering the same code into two radios is you have to chase down the other radio to get it to quit alarming. And if you choose to have unique MMSIs, make sure you install the radios in a way that you can determine which one is ringing. We have a buddy that has two identical radios installed one on top of the other and he goes mad trying to figure out which one is ringing...lol.

================================================== ============

This is exactly the situation my friend is trying to avoid.* Has your*buddy given thought to separate external speakers that are far enough apart so that they can be easily associated with the correct radio?* My follow on question is why don't they both alarm at the same time and why can't he look at the display to determine whats up?
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Old 04-11-2011, 11:42 AM   #7
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RE: Multiple DSC radio operation

Baker,

My MMSI number was issued by the FCC as a part of my station license. I don't think the FCC would issue 2 numbers to the same boat. I don't know about a Boat US number, maybe that's what he has.

In BC, Canada, the Canadian CG uses the DSC alarm to alert boaters to an emergency or to severe weather. I have had the alarm go off at least once per summer and sometimes more often.

If both radios have the same MMSI number, all that is required is to shut off, (power down) one radio, and then respond to the alarm on the other.

If the alarm is not an emergency alarm, but is a ringing indicating an incoming call, it goes to the VHF being 'dialed'. Having 2 MMSI numbers on two different radios could cause confusion, but as Ed said, looking at the display should clear up the problem.
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